Electrical generator parallel rings are used to remove power from an electrical generator during power plant operation. They are manufactured from copper pipe. During fabrication of the electrical generator parallel rings at a manufacturers facility, resin, used in another part of the fabrication process, may be accidentally introduced to the inside of the parallel ring piping. During fabrication the resin flows around the inside of the pipe to low points of the system and creates blockages within the pipes. Hydrogen flows to provide cooling, at relatively low pressure, through the inside of these pipes. The flow of hydrogen, pipe vibration or some other means may cause the resin to become dislodged and block the hydrogen flow path, resulting in overheating of the parallel ring pipes. Overheating of the pipes in the parallel ring could also lead to changes in electrical resistance which can create electrical issues with the generator.
Parallel rings are typically fabricated from approximately 2.25 in. OD×0.500 in. wall copper piping. Six pipes may comprise the parallel ring assembly and each of the pipes typically has a total arc length of approximately 90 degrees. Each of these pipes may have two inlets, one on each end of each pipe, and one exit point, in the middle of the pipe.
Due to the orientation of the ends of the pipes, with multiple 90° bends along their length, it is not possible to use standard pipe cleaning tooling to remove the resin. In addition, resin removal may be required in the 90° bends. Standard tooling used to clean straight, or slightly curved sections of pipe include brushes, scrapers, cone cutters, flexible hones, and flare brushes. These tools can be purchased from companies such as Goodway Technologies. Inside diameter tooling may also be used to cut heat exchanger tubes. These tools have been used in tubes from ⅝″ to 1″ diameter and are all driven by the same high speed motor that is used for resin removal while the cutting tip rotational speed is monitored with a tachometer.
None of the standard pipe cleaning tools mentioned above are flexible enough to negotiate the tight bends of parallel rings. In addition, most of these tools are used at relatively low speeds (approximately 2000-3000 RPM). Due to the thickness and adhesion of some of the resin deposited in parallel rings, tools spinning at this relatively low speed may not effectively remove the resin. Further, some of these tools may damage the inside surface of the parallel ring piping due to their aggressive design.